Today, IP-based network services are often offered over several types of network technologies, such as General Packet Radio Service (GPRS), Wireless Local Area Network (WLAN), Wideband Code Division Multiple Access (WCDMA), xDSL, cable modem, and Ethernet. Many mobile user devices are provided with multiple access interfaces to be able to make the most of this situation. Multi-access communication systems are generally more flexible than single-access networks but they also introduces an additional degree of complexity and involves a number of new requirements, choices and considerations.
General aspects of multi-access networks are addressed by the Always Best Connected (ABC) concept [1], [2], which envisions a communication environment where the user is always connected over the best available access network and device. The overall ABC concept can be seen as a framework of requirements:                Always—at any point in time, the user shall obtain the best communication experience.        Best—refers to the user experience. The best experience might, for instance, refer to the cheapest access network, the best application performance, the highest bandwidth, or the best device in combination with access and applications. What is best thus depends on user perception and in technical terms also on a combination of network characteristics, cost, device capabilities, application requirements, operator policies etc.        Connected—it is important to consider both what/whom the user is connected to, for example an application server, a corporate network, the Internet, another person, or another machine, and what/whom the user connected through, such as devices, a personal area network (PAN), access networks, backbones, the Internet etc. All of these entities and networks may affect the user experience.        
Designing solutions for scenarios like ABC includes consideration of different business scenarios, different architecture options, and different technical solutions. Hereby, important areas are: (i) subscription handling and infrastructures for authentication/authorization; (ii) service availability; (iii) service adaptation across multiple different accesses and different devices; (iv) mobility management; (v) distributed terminals/devices—PANs; (vi) access availability; and (vii) how to choose access, including how to define “best” [1]. This document primarily addresses aspects of the last area (vii) of access choice/selection.
Solutions for access selection in IP-based multi-access communication systems in the prior art often involve an active decision as for which access network to use by the end user effected through the graphical user interface (GUI) of his/her device. Alternatively, or in addition thereto, the multi-access terminal comprises a default priority list that is compared with currently available accesses
The International Patent Application WO 01/35585 A1 [3] proposes a mechanism for access-selection based on individual user preferences. The end device identifies available access networks and uses an indirect interface, such as a Bluetooth radio interface, to determine their respective access capability (cost of access, available bandwidth, etc.). The determined access capability is compared to a preferred access capability of the end device/user, which is stored at the end device and can be updated by the user. After all available access networks have been checked a best access is selected. The end device may continue to look for new available access networks and reconsider its access decision during a connection.
The conventional access selection methods are typically associated with rather heavy demands on both the end user and on his/her user equipment. Moreover, for a proper access selection many factors have to be considered and it can often be difficult for the user/terminal to obtain all information needed as well as to analyze complex access situations.
Particularly demanding arc cases where the mobile multi-access terminal resides in a car or another vehicle. Such vehicle scenarios typically require fast access selections and handoffs in order to maintain optimal access and avoid lost calls/sessions due to changed access situations. An access selection mechanism capable of handling vehicle scenarios satisfactory would thus be very desirable.
Accordingly, there is a considerable need for an improved method for access selection in multi-access networks.